1. Field of the Invention
The present invention relates to an insulating (isolating) transformer apparatus for ensuring safety against a leakage current of an electric device.
2. Description of the Related Art
Recently, medical systems have been widely employed in the field of medical treatment. These systems can have a plurality of medical electric devices (hereinafter, referred to as "ME device"), rather than a single ME device, which are combined, or a single ME device can be combined with other general electric devices.
Regarding the ME device, safety standards for leakage current (not a functional current, i.e., an unintentionally produced current) have been established and countermeasures thereto have been devised, in order to protect a patient against an electric shock caused when a doctor or an assistant touches the ME device and the patient.
Such safety standards or countermeasures, however, are not provided for general electric devices other than the ME devices. Thus, a leakage current higher than an allowable value defined in the safety standards for ME device may occur in a general electric device, which may endanger a patient.
Under these circumstances, an isolating transformer apparatus, as described below, has conventionally been connected between a commercial power source and a general electric device, thereby reducing leakage current from the general electric device.
The conventional transformer apparatus comprises a transformer, which includes a primary winding connected to the commercial power source and a secondary winding insulated from the primary winding, and a power source socket connected to the secondary winding of the transformer. A power source plug of a general electric device is connected to the power source socket.
In the case of the conventional isolating transformer apparatus, there is a concern that a user may erroneously pull out the power source plug of the electric device from the isolating transformer apparatus, and may connect it to a wall socket (i.e., a socket for medical use connected to the commercial power source).
In such a case, a leakage current higher than the allowable value may occur in the general electric device, and a patient may suffer an electric shock through a doctor or an assistant who has touched the ME device, as mentioned above.